A QFN (Quad Flat Non-leaded package) can be taken as an example of a resin package in which a semiconductor die mounted on a lead frame is encapsulated in a plastic package made of molding resin.
In the QFN, tip portions of a plurality of leads electrically connected to a semiconductor die via bonding wires are exposed from a rear surface (lower surface) of a peripheral part of a plastic package, by which terminals are formed. Also, bonding wires are connected to the surfaces opposite to the surfaces on which the terminals are exposed. More specifically, bonding wires are connected to the terminal surfaces inside the plastic package, by which the terminals and the semiconductor die are electrically connected to each other. The QFN is mounted on a wiring board by soldering these terminals to electrodes (footprint) on the wiring board. This structure of the QFN enables to obtain the advantage that the size of the mounting area can be reduced in comparison to a QFP (Quad Flat Package) in which the leads transversely extending from the side surfaces of a package (plastic package) constitute the terminals.
The descriptions of the QFN can be found in Japanese Patent Laid-Open No. 2001-189410 (corresponding U.S. Pat. No. 6,399,423) and Japanese Patent No. 3072291.